Abstract: An air to air heat exchange system for removing undesirable air from an enclosed structure. The heat exchanger provides for the removable of air containing pollutants, toxics gases and odors while providing for the recovery of heat from the exhaust air. The system utilizes a plurality of tubes within a larger tube so that air can flow freely over and around the smaller tubes thus providing for maximum heat transfer between the incoming air in the smaller tubes and the exhaust air in the larger tube. The smaller tubes, if used for the incoming air, permit the air to be distributed to various selected locations throughout the structure.

Abstract: An earth/block air preconditioner for use in dwellings and other buildings wherein the outside air is drawn below ground and passed through concrete blocks which are preformed with a pair of openings so that the outside air and inside air from the building are in close proximity so as to heat the outside air during the winter time due to the heat exchange arrangement with the inside air before passing it into the building and to cool the outside air during the summer time before passing it into the building. Modern buildings are insulated so tightly that forced ventilation is desirable and the present invention provides highly efficient heating and cooling or ventilation modes for a heat exchange system.